This invention relates to a mapping-type optimization system for reducing computer-network data traffic between (1) an arbitrary host unit, such as a VTAM application program, which issues SEND- and RECEIVE-type instructions to a communications manager such as VTAM; and a peripheral unit such as a remote terminal. In part, the invention represents an advantageous generalization of mapping-type optimization systems taught in U.S. Pat. No. 4,750,137; 4,837,679; 4,937,739; 5,005,137; and 5,046,025, all assigned to the assignee of this application.